Atrial fibrillation is a common form of cardiac arrhythmia. Although not all details on the mechanism of atrial fibrillation are clear at present, it has been observed that atrial fibrillation is often triggered from the pulmonary veins (PV). Atrial fibrillation may be treated by electrically isolating the pulmonary veins from the heart, e.g. from the left atrium, for example by applying catheter-based radiofrequency ablation around the pulmonary veins. Such therapeutic strategy may be particularly useful for patients with drug-resistant and symptomatic recurrent atrial fibrillation. For the ablation therapy to be successful, a good electrical isolation, e.g. substantially complete or complete electrical isolation, of the pulmonary veins is required.
It is known in the art that such electrical isolation can be verified by examining electrogram data recorded at the junction between the pulmonary vein and the left atrium during the ablation procedure, for example bipolar electrograms obtained at the junction by a circular mapping catheter, e.g. LASSO electrocardiogram data. The electrogram data contain far field potentials (FFP) generated by other anatomical structures in the heart, such as the atria, the left atrium appendage, the mitral annulus and the ventricles. When the electrical isolation between the pulmonary vein and the left atrium is insufficient, the electrograms contain both pulmonary vein potentials and far field potentials. On the other hand, when the pulmonary vein is isolated from the left atrium, the atrial electric signals cannot propagate into the pulmonary vein, such that the electrograms only contain far field potentials.
However, interpretation of such electrograms can be a challenging and time-consuming task, even to experienced electrophysiologists. Evaluation of the electrical isolation by visual assessment of the left atrium-pulmonary vein junction (LA-PV) electrogram data may also be assisted by pacing, for example by actively applying an electrical signal and checking whether this signal propagates across an isolation region, e.g. an ablation scar line provided for electrically isolating the pulmonary vein.
Other methods are known in the art for evaluating the electrical isolation indirectly, for example by imaging the lesion formed by the ablation process, e.g. using magnetic resonance imaging or ultrasound imaging. Although such methods may allow a more efficient evaluation, the indirect inference of the electrical insulation condition by such methods may lead to larger lesions being created than necessary in order to account for an uncertainty in verifying a sufficient isolation, or may lead to ineffective treatment when a lesion only appears to be sufficient for electrically isolating the vein.
The present invention relates to the detection of this electrical isolation by automated analysis of electrogram data recorded at the junction between the left atrium of the heart and a pulmonary vein, e.g. recorded during a radio-frequency ablation procedure. Thus, a distinction is made in accordance with a decision algorithm between the case where the electrogram data comprises both pulmonary vein potentials and far field potentials, e.g. where the pulmonary vein is not electrically isolated, and the case where the electrogram data contains only far field potentials, e.g. where the pulmonary vein is electrically isolated.